Numerous hydraulically or pneumatically energized driving motors which convert static energy introduced by a pressure medium into rotary motion by means of axial, radial or rotary pistons are known. All the known drives have sliding elements near the boundaries of the expansion chambers. Unfortunately, such elements ordinarily require that the pressure medium have lubricating capability or necessitate separate lubrication.
Technical expense involved in the production of existing drives is relatively high. The great majority of the known systems is not practicable for disk connected air and, in general, low pressure energizing for reasons of both construction and expense. In the case of rotary piston (cell) motors generally used for compressed air drive, the efficiency and force are slight due to high friction loss and considerable loss from leakage. They are not usable for low numbers of revolutions.
Motors comprising expansion chambers which are supported on supporting surfaces have already been proposed but not placed on the market. Depending upon the type of construction, significant friction loss occurs in drive as a consequence of the relative movement of the chamber surface areas, especially the border sections. Those motors have the further disadvantage that tensile stress, with peaks of stress in the border areas of the chambers, also appears and results in significantly shortening the length of serviceability of such expansion chambers.